ospf multizone understanding

[Rowlands Sharles]

Hello support,

I have a question regarding ospf with multiple areas, it's possible to have a area dehind another area outside zone 0?

Attached is the diagram, can we have area 10 ?

Thanks

[MHM Cisco World · Accepted solution]

Yes you can use virtual link

https://www.cisco.com/c/en/us/support/docs/ip/open-shortest-path-first-ospf/47866-ospfdb7.html

MHM

[Rowlands Sharles]

Okay, that means if you use this scenario, you must therefore use the virtual link?

[MHM Cisco World · Accepted solution]

Yes You need it since area 10 can not direct connect to backbone area 0

MHM

[Rowlands Sharles]

Okay, many thanks, will read the document sent.

[Rowlands Sharles]

Hello,

Last thing please, how can i know the number of routers in an area?

[Robert Plunkett · Accepted solution]

Remember, when creating your virtual link you should use you ospf router ID.

[Torbjørn]

@MHM Cisco World is correct that a virtual link can be used to achieve this. I just want to add that you should avoid this situation if possible. If you do find yourself in a situation where you have to use a virtual link, you should only rely on this as a temporary fix.